Distributed turbo encoder and method

ABSTRACT

The present disclosure relates to an apparatus and method supportive of distributed turbo coding based on relay network utilizing a noisy network coding scheme. For this, included is a relay node operating as a component encoder to relay a signal from a source node to a next node in a distributed turbo coding scheme. The relay node quantizes the signal transmitted from the source node and then interleaves the quantized signal using a predetermined pattern to distinguish the signal transmitted from the source node from a signal to be output from an opposing node, so that the signal transmitted from the source node is relayed to the next node based on a noisy network coding scheme.

CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

The present application is related to and claims the benefit under 35U.S.C. §119(a) of a Korean patent application filed in the KoreanIntellectual Property Office on May 8, 2014 and assigned Serial No.10-2014-0054851, the entire disclosure of which is incorporated hereinby reference.

TECHNICAL HELD

The present disclosure relates to distributed turbo coding apparatusesand methods for multi-transmission in a mobile communication system.

BACKGROUND

To meet the demand for wireless data traffic having increased sincedeployment of 4G (4th-Generation) communication systems, efforts havebeen made to develop an improved 5G (5th-Generation) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

in addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier(FBMC), non-orthogonal multipleaccess(NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

in a typical wireless communication system, terminals positioned inareas with poor signal quality, such as cell boundaries or shadow areas,are difficult to serve with seamless communication services from basestations.

To address this issue, more attention is paid to relay networks thatbring up with expanded service coverage and increased system capacity. Arelay network means a network that expands service coverage with relaynodes. A relay node receives signals from a source node and transfersthe received signals to other relay node or a destination node. Thetechnique in which a relay node relays signals between a source node andother relay node or a destination node is denoted a “multi-hoptransmission.”

A representative relay network-related technique is IEEE 802.15.3-basedwireless personal area network (WPAN).

Various schemes are being prepared to equip relay network with increasednetwork capacity, reduced channel usage count along with steadycommunication performance.

Among such relay network-related schemes, noisy network coding has beenproposed to obtain a communication performance that approaches thechannel capacity. Noisy network coding is among the schemes forutilizing relay nodes in a relay network.

According to this scheme, a relay node in a relay network receivesanalog signals from a source node, quantizes the received analog signal,converts into digital signals, channel-codes, and transmits theresultant signals to a next node.

The noisy network coding scheme keeps the gap between a theoreticalchannel capacity achievable from a relay network and the upper-boundchannel capacity at a predetermined value.

Upon adopting the noisy network coding scheme, the relay node conductstwo stages of computation in order to transfer received signals to anext node. The first stage is to quantize the signals received from thesource node, and the second is to map the quantized signals toparticular symbols and transmit the mapped signals to the next node. Forexample, the next node is an other relay node or a destination node.

The relay node, upon the second stage of computation, conducts channelcoding on the quantized signals. A low density generator matrix (LDGM)or LDPC code comes in use for the channel coding.

The following documents are related to the channel coding performed bythe relay node.

[1] “Coding and System Design for Quantize-Map-and-Forward Relaying,”IEEE Journal on Selected Areas in Communications, V. Nagpal, et al, 11,November 2013, 1423-1435

[2] “Graph-based Codes for Quantize-Map-and-Forward Relaying,” IEEEinformation Theory Workshop, A. Sengupta, et al, 16-20, October 2011,140-144

[3] “Turbo-Like Codes for Transmission of Correlated Sources over NoisyChannels,” IEEE Signal Processing magazine, Garcia-Frias J., et al,September 2007, 58-66

[4] “Compression of Correlated Binary Sources Using Turbo Codes,” IEEECommunications Letters, Garcia-Frias J., et al, October 2001, 417-419

Document [1] supra proposes the optimization of channel codes used intransmitting nodes and relay nodes. Pursuant to Document [1], there is asingle relay node; the destination node uses multiple antennas; and thesource node and relay node adopt the diagonal-bell laboratory layeredspace-time (D-BLAST) scheme for signal transmission. The optimizationset forth in Document [1] applies to the receiving node independentlyobserving signals respectively transmitted from the source node and therelay node. In other words, this scheme is difficult to apply to generalrelay networks.

Document [2] discloses selecting the best performing component codethrough repetitive simulations and allowing the relay node to use thesame. Document [2], however, fails to suggest a generalized design toput the best performing component code to use.

Document [3] concerns use of LDGM codes to maintain the correlationbetween information items respectively observed by terminals, Thetechnique set forth in Document [3] makes use of LDGM codes, in parallelor in a sequential and consecutive way, in order to address the higherror floor issue that arises due to the low order of LDGM matrix.

Document [4] bears similar research results to those of Document [3],Document [4] discloses using convolutional codes that are in parallel orsequentially consecutive with each other. Use of such distributed turbocodes (turbo-like codes) causes the joint decoding by the destinationnode to be too complicated, and in some cases, cannot guarantee theoptimized relay network.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

To address the above-discussed deficiencies, it is a primary object toprovide the design architecture of a source, destination, and relay nodewith a performance approaching the optimal channel capacity in a relaynode utilizing a noisy network coding scheme.

A proposed embodiment provides an apparatus and method supportive ofdistributed turbo coding based on relay network utilizing a noisynetwork coding scheme.

A proposed embodiment provides a channel coding and mapping apparatusand method that is performed by a relay node in a relay networkutilizing a noisy network coding scheme.

A proposed embodiment suggests a mapping scheme by a relay node to allowa destination node to obtain a combining gain in a relay networkutilizing a noisy network coding scheme.

A proposed embodiment provides a channel coding apparatus and methodthat is optimized while exhibiting a performance approaching the channelcapacity without increasing complexity in a relay network utilizing anoisy network coding scheme.

A proposed embodiment provides an apparatus and method for allowing arelay node, constituting a relay network utilizing a noisy networkcoding scheme, to perform, as a component code encoder, distributedturbo coding on the relay network.

According to a proposed embodiment, a relay network comprises a relaynode operating as a component encoder to relay a signal transmitted froma source node to a next node in a distributed turbo coding scheme. Therelay node quantizes the signal transmitted from the source node andthen interleaves the quantized signal using a predetermined pattern todistinguish the signal transmitted from the source node from a signal tobe output from an opposing node, so that the signal transmitted from thesource node is relayed to the next node based on a noisy network codingscheme.

According to a proposed embodiment, a method for relaying a signal in arelay network comprises, upon relaying a signal transmitted from asource node to a next node in a distributed turbo coding scheme, a relaynode operating as a component encoder so that the signal transmittedfrom the source node is relayed to the next node based on a noisynetwork coding scheme.

Operating as the component encoder includes the relay node quantizingthe signal transmitted from the source node and interleaving thequantized signal using a predetermined pattern to distinguish the signaltransmitted from the source node from a signal to be output from anopposing node.

According to a proposed embodiment, the relay network utilizing thenoisy network coding scheme secures an enhanced performance withoutsharp increases in complexity in the relay network while optimizingcomponent codes using a well-known optimizing method such as extrinsicinformation transfer (EXIT) chart.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same, It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely,Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates the configuration of an exemplary relay networksupportive of distributed turbo coding according to various embodimentsof the present disclosure;

FIG. 2 illustrates the configuration of an exemplar conventional turbodecoder according to various embodiments of the present disclosure;

FIG. 3 illustrates an exemplary configuration supportive of distributedturbo coding in a relay network adopting a noisy coding scheme accordingto various embodiments of the present disclosure;

FIG. 4 illustrates a configuration for providing distributed turbocoding in a relay network according to various embodiments of thepresent disclosure;

FIG. 5 illustrates the configuration of an exemplary destination node ina relay network according to various embodiments of the presentdisclosure;

FIG. 6 illustrates bit reordering according to various embodiments ofthe present disclosure;

FIGS. 7A and 79 illustrate an exemplary operation of a combining mapperaccording to various embodiments of the present disclosure; and

FIG. 8 illustrates experimental data obtained by analyzing an existingsystem and a system according to various embodiments of the presentdisclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

FIGS. 1 through 8, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged wireless communication device.

According to various embodiments of the present disclosure, thedestination node receives signals from a plurality of nodes and performsjoint decoding on the received signals to thus restore desired signals.The plurality of nodes includes at least one relay node. For example,when one of two nodes is a relay node, the other can be a source node.The plurality of nodes can be all relay nodes.

As described above, at least two signals received by the destinationnode should be consistent with each other in the position of thesystematic bits constituting the signals so that the destination nodeObtains a combining gain by the systematic bits respectively included inthe two signals.

Proposed embodiments are now described in more detail with reference tothe accompanying drawings.

FIG. 1 illustrates an exemplary configuration of a relay networksupportive of distributed turbo coding according to various embodimentsof the present disclosure.

Referring to FIG. 1, first and second component encoders 110 and 130respectively correspond to relay nodes. The relay node corresponding tothe second component encoder 130 include an interleaver. A source node,instead of the relay node, plays a role as the first component encoder110. In certain embodiments, the source node is able to quantizesignals, encode and. symbol-map the quantized signals, and transmit thesame. For ease of description, the first component encoder 110 is arelay node.

The source node and destination node constituting a relay network arenot illustrated in FIG. 1. FIG. 1 merely illustrates a signal (message)transmitted from a source node to the first component encoder 110 andthe interleaver 120. Illustrates an input signal (m), a signal (c₁)output from the first component encoder 110, and a signal (c₂) outputfrom the second component encoder 130. Hereinafter, the signal inputfrom the source node is denoted an “information signal,” “informationbit stream,” or “information bits,” and the signals output from thefirst component encoder 110 and the second component encoder 130 arecollectively denoted an “extra signal,” “extra bit stream,” or “extrabits.” In particular, the signal (c₁) output from the first componentencoder 110 is denoted a “first extra signal,” “first bit stream,” or“first extra bits,” and the signal (c₂) output from the second componentencoder 130 is denoted a “second extra signal,” “second extra bitstream,” or “second extra bits,” The area where information bits arepositioned in a particular signal is denoted an “information part,” andthe area where extra bits are positioned in the signal is denoted an“extra part.” In the same technical field, an information bit can bedenoted a “systematic bit,” and an extra bit can be denoted a “paritybit.”

The first extra signal (c₁) is a signal generated by quantizing theinformation signal (m), encoding the quantized signal, and thensymbol-mapping the encoded signal. The second extra signal (C₂) is asignal generated by quantizing an interleaved information signal (m′),encoding the quantized signal, and the symbol-mapping the encodedsignal. The interleaved information signal (m′) is a signal generated bythe interleaver 120 interleaving the (m) with a predetermined pattern.

The information signal (m) is shown as if the information signal (m) isoutput separately from the first and second extra signals (c₁, c₂). Incertain embodiments, however, the first component encoder 110 outputs acombined signal of information bits and first extra bits, and the secondcomponent encoder 130 outputs a combined signal of information bits andsecond extra bits.

The information bits in the signal output from the first componentencoder 110 and the information bits in the signal output from thesecond component encoder 130 are ordered at the same positions. Theextra bits in the signal output from the first component encoder 110 andthe extra bits in the signal output from the second component encoder130 are ordered at different positions.

As described above, the reason for positioning the information bits andextra bits in the signals output from the first and second componentencoders 110 and 130 is to allow the destination node to obtain acombining gain. The specific operation of the first and second componentencoders 110 and 130 generating extra signals to allow a combining gainto be obtained is described below. The specific configuration of extrasignals generated by the first and second component encoders 110 and 130is also described below.

FIG. 2 illustrates the configuration of an exemplary conventional turbodecoder according to various embodiments of the present disclosure. Theturbo decoder illustrated in FIG. 2 is an example of a parallelconcatenated decoder.

Referring to FIG. 2, a signal (y) input to the turbo decoder includes aninformation part (m) where information bits are positioned and two extraparts (c₁, c₂) where extra bits are positioned. A first componentdecoder 210 decodes a prior information bit stream (m), the informationpart (m), and one extra part (c₁) to output a decoded information bitstream (m).

An interleaver 220 interleaves the information bit stream (m) outputfrom the first component decoder 210 by using a predetermined patternand outputs the interleaved information bit stream (m′). As an example,the interleaver 220 interleaves the information bit stream (m) to fit anindex of a second component decoder 230.

The second component decoder 230 performs decoding based on an inputsignal including the interleaved information bit stream (m)corresponding to the prior information bit stream, the information part(m), and the other extra part (c₂) and outputs an information bitstream. as the result of the decoding. The information bit streamdecoded by the second component decoder 230 is input to a deinterleaver240.

The deinterleaver 240 deinterleaves the information bit stream inputfrom the second component decoder 230 by using a predetermined pattern.As an example, the deinterleaver 240 interleaves the information bitstream (m) to fit an index of the first component decoder 210,

The information bit stream (m) deinterleaved by the deinterleaver 240 isinput as a prior information bit stream of the first component decoder210. The information bit stream (m) output from the deinterleaver 240and the information bit stream (m) output from the first componentdecoder 210 are added by an adder in units of bits, outputting aprediction information bit stream ({circumflex over (m)}).

The above-described operation of the turbo decoder can be repeatedlyperformed in a predetermined number of times, and a final message bethereby estimated.

FIG. 3 illustrates an exemplary configuration supportive of distributedturbo coding in a relay network adopting a noisy coding scheme accordingto various embodiments of the present disclosure. Although FIG. 3illustrates the configuration as implemented with two relay nodes, theconfiguration can be implemented with three or more relay nodes as well.

Referring to FIG. 3, a hop is present between a source node 310 and adestination node 350. In other words, only one relay network exists foreach path connecting the source node 310 with the destination node 350.In certain embodiments, relay nodes corresponding to two or more hopsare present on a path connecting the source node 310 with thedestination node 350.

The source node 310 transmits analog signals. The signals transmittedfrom the source node 310 are received by the relay nodes 320 and 330,respectively. The signals respectively received by the relay nodes 320and 330 include different channel features g21 (312) and g31 (314),respectively. For example, the signal received by the first relay node320 is a signal including the signal transmitted from the source node310 and the channel feature g21 (312), and the signal received by thesecond relay node 330 is a signal including the signal transmitted fromthe source node 310 and the channel feature g31 (314).

The first and second relay nodes 320 and 330 process the receivedsignals considering noisy network coding and distributed turbo coding.By way of example, the first and second relay nodes 320 and 330 conductquantization, encoding, and symbol-mapping on the received signals tosupport noisy network coding.

In order for the distributed turbo coding, the information bit streaminput for encoding in the first relay node 320 differs in order from theinformation bit stream input fir encoding in the second relay node 330.The first relay node 320 performs encoding on a quantized bit streamwhile the second relay node 330 interleaves a quantized bit stream andthen encodes the interleaved bit stream.

As a result of the encoding, a first output signal output from the firstrelay node 320 can be different in bit order from a second output signaloutput from the second relay node 330. Preferably, the information bitsin the first output signal should be the same in order as theinformation bits in the second output signal. Putting the first outputsignal and the second output signal in the same order of informationbits is for allowing the destination node 350 to have a combining gain.

Nevertheless, it is not that the extra bits in the first output signaland the second output signal should be placed in different orders. Thisis why the bits input for encoding in the first relay node 320 differ inorder from the bits input for encoding in the second relay node 330.

The signals generated by the first and second relay nodes 320 and 330are transmitted to the destination node 350. The signals transmitted bythe first and second relay nodes 320 and 330 are mixed (340) on a radiochannel and are received by the destination node 350. The signals thatare transmitted from the first and second relay nodes 320 and 330,respectively, and received by the destination node 350 have differentchannel features h42 (322) and h43 (332), respectively.

The destination node 350 performs joint decoding the signals receivedfrom the first and second relay nodes 320 and 330 through a multipleaccess channel (MAC). The destination node 350 obtains information,which the source node 310 intends to transfer, through the jointdecoding.

FIG. 4 illustrates a configuration for providing distributed turbocoding in a relay network according to various embodiments of thepresent disclosure. Although assuming two relay nodes as shown in FIG.4, the configuration comes up with one, two or more relay nodes.

Referring to FIG. 4, the configuration for offering distributed turbocoding includes a quantizing means, a distributed turbo encoder 430, anda combining mapper 440.

The quantizing means is configured with quantizers 411 and 421respectively provided in the relay nodes 410 and 420. The quantizers 411and 421 quantize analog input signals into digital signals.

The distributed turbo encoder 430 receives a plurality of quantizedsignals predicted to have the same bit order, adjusts the quantizedsignals to have different bit orders, and then encodes the resultantsignals.

For example, the distributed turbo encoder 430 interleaves a quantizedsignal from one of the two relay nodes 410 and 420 in order to allowquantized signals, which are subject to encoding for the relay nodes,respectively, to have different bit orders. That is, the signal (m₁m₂ .. . m_(k)) quantized by the first quantizer 411 is encoded by an RSCencoder 413. However, the signal (m₁m₂ . . . m_(k)) quantized by thesecond quantizer 421 is interleaved by an interleaver 423 using apredetermined pattern (interleaving pattern) before encoded by an RSCencoder 425. As described supra, it can be verified that the signal(m₁m₂ . . . m_(k)), quantized by the first quantizer 411, and the signal(m_(i)m_(j) . . . m₁), quantized by the second quantizer 421 and theninterleaved, have different orders of information bits.

Accordingly, the encoded bit stream output from the RSC encoder 413 ofthe first relay node 410 and the encoded bit stream output from the RSCencoder 425 can have different bit orders as well. In certainembodiments, the encoded bit stream output from the first RSC encoder413 is m₁c₁ ¹m₂c₂ ¹ . . . m_(k)c_(k) ¹, and the encoded bit streamoutput from the second RSC encoder 425 is m_(i)c_(j) ²m_(i)c_(j) ² . . .m₁c₁ ². As such, the two encoded bit streams are identified to havedifferent bit orders. It can be particularly verified that theinformation bits constituting the encoded bit streams have differentpositions.

The first and second RSC encoders 413 and 425 are presumed to userecursive systematic convolutional (RSC) codes.

The combining mapper 440, which includes mapper 440, mapper 429, andreordering unit 427, operates as a symbol mapper to allow a signal,supposed to be received by the destination node, to obtain a combininggain. The combining gain should be obtained targeting information bits.The information bits constituting the encoded bit stream of the firstRSC encoder 413 are thus required to be consistent in position with theinformation bits constituting the encoded bit stream of the second RSCencoder 425 before symbol mapping in each relay node 410 and 420 inorder to allow the combining gain to be obtained.

Bit reordering is carried out to allow the order (m₁m₂ . . . m_(k)) ofinformation bits in the encoded bit stream m₂c₂ ¹m₂c₂ ¹ . . . m_(k)c_(k)¹ output from the first RSC encoder 413 to be consistent with the order(m_(i)m_(j) . . . m_(j)) of information bits in the encoded bit streamm₁c₁ ²m_(i)c_(j) ² . . . m₁c₁ ² output from the second RSC encoder 425.

As an example, the second relay node 420 has a rearranging unit 427 toreorder the position of the encoded bits. The rearranging unit 427 isprovided with a (predetermined pattern (interleaving pattern) as used inthe interleaver 423 in order to reorder the encoded bits. Therearranging unit 427 reorders the order (m_(i)m_(j) . . . m_(j)) ofinformation bits in the encoded bit stream m_(i)c_(i) ²m_(j)c_(j) ² . .. m_(i)c_(j) ² output from the second RSC encoder 425 to be consistentwith the order (m₂m₂ . . . m_(k)) of information bits in the encoded bitstream m₁c₂ ¹m₂c₂ ¹ . . . m_(k)c_(k) ¹ output from the first RSC encoder413. Hence, the encoded bit stream m₁c₁ ²m₂c₁ ² . . . m_(k)c₁ ² outputfrom the rearranging unit 427 is the same in order of information bitsas the encoded bit stream m₂c₂ ¹m₂c₂ ¹ . . . m_(k)c_(k) ¹ output fromthe first RSC encoder 413. In certain embodiments, the extra bits in theencoded bit stream m₁c₁ ²m₂c_(j) ² . . . m_(k)c₁ ² output from therearranging unit 427 have different values than those of the extra bitsin the encoded bit stream m₁c₁ ¹m₂c₂ ¹ . . . m_(k)c_(k) ¹ output fromthe first RSC encoder 413.

FIG. 6 illustrates bit reordering according to various embodiments ofthe present disclosure.

Referring to Fig, 6, it be identified that an encoded bit stream m₁c₁¹m₂c₂ ¹ . . . m_(k)c_(k) ¹ output output from an RSC encoder 413provided in a first relay node 410 has no correlation with an encodedbit stream m₁c₁ ²m_(j)c_(j) ² . . . m_(j)c_(j) ² output from an RSCencoder 425 provided in a second relay node 420 due to an influence byan interleaver. In order to recover the inter-bit correlation, theencoded bit stream m₁c₁ ²m_(j)c_(j) ² . . . m_(j)c_(j) ² output from theRSC encoder 425 provided in the second relay node 420 is reordered forthe position of information bits, outputting an encoded bit stream m₁c₁²m₂c₁ ² . . . m_(k)c₁ ².

Accordingly, it is verified that the encoded bit stream m₁c₁ ²m₂c₂ ¹ . .. m_(k)c_(k) ¹ in the first relay node 410 is the same as the encodedbit stream m₁c₁ ²m₂c₁ ² . . . m_(k)c₁ ² in the second relay node 420 forodd-numbered bits (information bits).

The encoded bit stream m₁c₁ ¹m₂c₂ ¹ . . . m_(k)c_(k) ¹ output from theRSC encoder 413 provided in the first relay node 410 and the encoded bitstream m₁c₁ ²m₂c₁ ² . . . m_(k)c₁ ², output from the RSC encoder 425provided in the second relay node 420 and bit-reordered, are subjectedto gray mapping. The gray mapping is conducted by mapping the encodedbit streams to gray codes. The signals transmitted from the relay nodesare rendered to have the same information part.

FIGS. 7A and 7B illustrate an exemplary operation of a combining mapperaccording to various embodiments of the present disclosure.

FIG. 7A illustrates an example in which an encoded bit stream is mappedto one symbol in each unit of two bits and is output, and FIG. 7Billustrates an example in which an encoded bit stream is mapped to onesymbol in each unit of four bits and is output.

As set forth above, applying gray mapping to encoded bits increases thesimilarity between symbols respectively transmitted from the relaynodes, allowing the destination node a combining gain.

Unless a combining buffer 440 is used as the symbol mapper, the messagesrespectively transmitted from the relay nodes 410 and 420 areinterleaved by a random interleaver, turning into independent signalsfrom each other. This also cause the extra parts, which have passedthrough the RSC encoders, to be not correlated with each other,resultantly preventing the destination node from being allowed acombining gain,

FIG. 5 illustrates the configuration of an exemplary destination node ina relay network according to various embodiments of the presentdisclosure. In particular, FIG. 5 illustrates the configuration of adistributed turbo decoder decoding encoded signals transmitted forsupporting a distributed turbo coding scheme.

The distributed turbo decoder illustrated in 5 operates similar togeneral-type turbo decoders. However, the proposed distributed turbodecoder is differentiated from the general-type turbo decoders byexchanging extrinsic information between component decoders through adecoder corresponding to a channel coder in a transmitting node.

Referring to FIG. 5, a log-likelihood radio (LIR) computing unit 510computes LLRs for each relay node using a signal (y) received through anMAC. The UR computing unit 510 is additionally input with change valuesof consecutive encoded bits per relay node in order to compute LLRs foreach relay node. For example, the change values of the encoded bits froma first relay node are output values from a subtractor 512 and thechange values of the encoded bits from a second relay node are outputvalues that are output from the subtractor 514 and that arebit-reordered by a bit rearranging unit 580. The change values of theconsecutive encoded bits per relay node are real numbers, rather thanbinary codes. For example, the change values of the consecutive encodedbits per relay node are defined as real numbers between 0 and 1.

Values c₁(i), c₂(i) respectively computed for the relay nodes by the LLRcomputing unit 510 are provided to their respective correspondingdecoders 520 and 530 for decoding. The values c₁(i), c₂(i) respectivelycomputed for the relay nodes correspond to encoded bit streams.

For example, the LLR computing unit 510 provides the LLR value c₁(i)computed corresponding to the first relay node to the first decoder 520and the LLR value c₂(i) computed corresponding to the second relay nodeto the second decoder 530. The LLR value c₂(i) computed. correspondingto the second relay node is anti-bit reordered by an anti-hit reorderingunit 570 and is then provided to the second decoder 530. The anti-bitreordering 570 is carried out to eliminate the influence of thecombining mapper.

The first and second decoders 520 and 530 are BUR decoders usingconvolutional codes.

In addition to c₁(i) provided from the LLR computing unit 510, theprior-restored. information bit m(i) is input to the first decoder 520.In addition to c₂(i) provided from the LLR computing unit 510, theprior-restored and interleaved information bit m′(i) is input to thesecond decoder 530.

The first decoder 520 performs decoding using the LLR value c₁(i)computed. corresponding to the first relay node and the prior-restoredinformation bit m(i) and outputs an information bit m(0) and an encodedbit c₁(0) by the decoding.

The second decoder 530 performs decoding using the LLR value c₂(i)computed corresponding to the second relay node and the prior-restoredand interleaved information bit m′(i) and outputs an information bitm′(0) and an encoded bit c₂(0) by the decoding.

The subtractor 512 subtracts the LLR value c₁(i) computed by the UR.computing unit 510 from the encoded bit c₁(0) output from the firstdecoder 520. Variations among consecutive encoded bits computed by thesubtractor 512 are provided to the LLR computing unit 510.

The subtractor 514 subtracts the LLR value c₂(i) computed by the LLRcomputing unit 510 from the encoded bit c₂(0) output from the seconddecoder 530. Variations among consecutive encoded bits computed by thesubtractor 514 are provided to the LLR computing unit 510.

The variations among the consecutive encoded bits computed by thesubtractor 514 are bit-reordered by a bit reordering unit 580 and arethen provided to the LLR computing unit 510.

The encoded bits c₁(0) and c₂(0) obtained through the first and seconddecoders 520 and 530 are extrinsic information of the whole sequence.The extrinsic information is utilized as prior information uponestimating the LLR values for the respective transmitting signals of therelay nodes in subsequent repetitions,

The information bits (m(0), in m′(0)) acquired through the first andsecond decoders 520 and 530 are used to decode channel codes in therelay nodes or source code. By way of example, assume that the LDPCdecoder 550 is a channel decoder corresponding to a relay node or sourcecode. Accordingly, the extrinsic information obtained through thechannel decoder is utilized as prior information in next repetitions byeach component decoder.

Specifically, the information bit m(0) obtained by the first decoder 520and the information bit m(0) obtained by deinterleaving the informationbit m′(0) obtained by the second decoder 530 are added together by theadder 522 and input to the LDPC decoder 550. The LDPC decoder 550restores the information bits using the input information bits.

A subtraction is performed by the subtractor 552 between the informationbit m(0) obtained by the first decoder 520 and the information bitrestored by the LDPC decoder 550. The subtractor 552 subtracts theinformation bit m(0) obtained by the first decoder 520 from theinformation bit restored by the LDPC decoder 550 and outputs the result.The resultant information bit output from the subtractor 552 is input tothe first decoder 520 as a prior information bit.

A subtraction is performed by the subtractor 554 between the informationbit restored by the LDPC decoder 550 and the information bit that isobtained by the second decoder 530 and that is then deinterleaved by thedeinterleaver 540. The subtractor 554 subtracts the information bit,which is obtained by the second decoder 530 and then deinterleaved bythe deinterleaver 540, from the information bit restored by the LDPCdecoder 550. The resultant information bit output from the subtractor554 is interleaved by the interleaver 560 and then input to the seconddecoder 530 as a prior information bit.

The above-described operation is repeatedly a predetermined number oftimes, and the transmitted message is estimated by the final valuesoutput from the channel decoder.

FIG. 8 illustrates experimental data obtained by analyzing an existingsystem and a system according to various embodiments of the presentdisclosure. It may be evident from FIG. 8 that the gain obtained by thesystem according to the embodiment is increased by about 0.7 dB ascompared with the gain obtained by the conventional system.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art, it is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A relay network, comprising a relay nodeoperating as a component encoder to relay a signal transmitted from asource node to a next node in a distributed turbo coding scheme, whereinthe relay node is configured to: quantize the signal transmitted fromthe source node; and interleave the quantized signal using apredetermined pattern to distinguish the signal transmitted from thesource node from a signal to be output from an opposing node, so thatthe signal transmitted from the source node is relayed to the next nodebased on a noisy network coding scheme.
 2. The relay network of claim I,wherein the relay node is further configured to: perform an encodingprocess on the interleaved signal; and perform combining mapping on asignal obtained by the encoding process to obtain a combining gain withthe signal to be output from the opposing node.
 3. The relay network ofclaim 2, wherein the relay node is further configured to perform thecombining mapping by performing bit reordering on information bitsconstituting the signal obtained by the encoding process to turn theinformation bits back to an order prior to interleaving and applyinggray mapping to the reordered information bits.
 4. The relay network ofclaim 3, wherein the relay node is further configured to perform theencoding process on the interleaved signal using a recursive systematicconvolutional (RSC) code.
 5. The relay network of claim 3, wherein therelay node is further configured to perform the bit reordering based onthe predetermined pattern.
 6. The relay network of claim 1, furthercomprising a destination node configured to: receive signals from aplurality of nodes by the distributed turbo coding scheme; andindependently apply convolutional code-based decoding to each of thesignals received from the plurality of nodes to thereby restore thesignals.
 7. The relay network of claim 6, wherein the destination nodeis further configured to: apply joint decoding to restore the signalsreceived from the plurality of nodes.
 8. The relay network of claim 1,wherein the opposing node is one of the source node and at least oneother relay node.
 9. The relay network of claim 8, wherein when theopposing node is the at least one other relay node, the opposing node isconfigured to: quantize the signal transmitted from the source node;perform an encoding process on the quantized signal; and performcombining mapping on a resultant signal.
 10. The relay network of claim1, wherein a signal output from the relay node and a signal output fromthe opposing node are in a same position of information bits as eachother.
 11. A method for relaying a signal in a relay network, the methodcomprising, upon relaying a signal transmitted from a source node to anext node in a distributed turbo coding scheme, operating a relay nodeas a component encoder so that the signal transmitted from the sourcenode be relayed to the next node based on a noisy network coding scheme,wherein operating as the component encoder comprises: quantizing, by therelay node, the signal transmitted from the source node; andinterleaving, by the relay node, the quantized signal using apredetermined pattern to distinguish the signal transmitted from thesource node from a signal to be output from an opposing node.
 12. Themethod of claim 11, wherein operating a relay node as the componentencoder further includes: performing an encoding process on theinterleaved signal; and performing combining mapping on a signalobtained by the encoding process to obtain a combining gain with thesignal to be output from the opposing node.
 13. The method of claim 12,wherein performing the combining mapping includes: performing thecombining mapping by performing bit reordering on information bitsconstituting the signal obtained by the encoding process to turn theinformation bits back to an order prior to interleaving; and applyinggray mapping to the reordered information bits.
 14. The method of claim13, wherein performing the encoding process is performing the encodingprocess on the interleaved signal using a recursive systematicconvolutional (RCA) code.
 15. The method of claim 13, wherein the bitreordering is performed based on the predetermined pattern.
 16. Themethod of claim 11, further comprising a destination node restoring asignal by receiving signals from a plurality of nodes by the distributedturbo coding scheme and independently applying convolutional code-baseddecoding to each of the signals received from the plurality of nodes.17. The method of claim 16, wherein the destination node applies jointdecoding to restore the signals received from the plurality of nodes.18. The method of claim 11, wherein the opposing node is one of thesource node and at least one other relay node.
 19. The method of claim18, further comprising in a case where the opposing node is the at leastone other relay node, the opposing node quantizing the signaltransmitted from the source node, performing an encoding process on thequantized signal, and then performing combining mapping on a resultantsignal.
 20. The method of claim 11, wherein a signal output from therelay node and a signal output from the opposing node are in a sameposition of information bits as each other.